Few psychological disorders in the Diagnostic Statistical Manual have generated as much controversy as Dissociative Identity Disorder (DID). For the past 35 years diagnoses of DID, previously referred to as Multiple Personality Disorder (MPD), have increased exponentially, causing various psychological researchers and clinicians to question the validity of this disorder. DID is, however, currently recognized by the DSM-IV-TR as a true psychological disorder that emerges, most commonly, as a result of early childhood sexual abuse (DSM-IV-TR, 1994; Haddock, 2001; Zimbardo, Johnson, & Weber, 2006; Comer, 2007; Lev-Wiesel, 2005). In this essay I will first provide background information on DID, and identify and define the terminology commonly associated with the disorder. Second, I will discuss treatment modality, in addition to options for health insurance coverage. Third, I will discuss the argument of Dr. August Piper and Harold Merskey that contradicts the validity of DID. And lastly, I will address the ethical importance of recognizing DID as a severe and complicated disorder that continues to defy a mechanistic definition.